Pressure sensors that use a semiconductor piezoresistance effect are small and light, and have high sensitivity, and thus are used broadly in fields such as industrial instrumentation and medicine. In this type of pressure sensor, a diaphragm is formed on a semiconductor substrate. Strain gages are formed on the diaphragm. The strain gages are deformed by pressure applied to the diaphragm. The pressure is measured by detecting the changes in resistances in the strain gages due to the piezoresistance effect.
There are known one-chip pressure sensors provided with a differential pressure diaphragm and a static pressure diaphragm on the same substrate (Japanese Unexamined Patent Application Publication H5-72069 (“JP '069”)). In this document, a strain isolating band is formed between a differential pressure strain gauge and a static pressure strain gauge. The formation of the strain isolating band prevents the stress that is produced in the static pressure diaphragm when a static pressure is applied from propagating to the differential pressure diaphragm, thereby preventing the differential pressure value from being influenced by the applied pressure. For example, when a differential pressure is applied, excess stress is produced in the sensor chip due to the deformation of the differential pressure diaphragm. The static pressure gauge is affected by this stress. Additionally, when a static pressure is applied, excess stress is produced in the sensor chip due to the deformation of the static pressure diaphragm. The differential pressure gauge is affected by this stress. These effects are reduced by the strain isolating band.
A pressure sensor of another structure has also been disclosed (Japanese Patent 3359493 (“JP '493”)). In this pressure sensor, a structure is used wherein appropriate non-bonded regions are provided at corner portions of a bonding surface between a sensor chip and a pedestal. Specifically, a differential pressure diaphragm is formed in the center of the sensor chip, and non-bonded regions are formed at the corner portions of the sensor chip. This makes it possible to reduce the zero shift due to temperature, and reduce the variability thereof, to produce excellent thermal characteristics.
However, JP '069, when the sensor chip is miniaturized it becomes difficult to secure adequate space for the strain isolating band. That is to say, the sensor chip is larger by the size of the strain isolating band. Additionally, when the structure in JP '493 is applied to a one-chip pressure sensor, it becomes difficult to secure space for the formation of the non-bonded regions at the corner portions of the sensor chip.
In this way, there is a problem in that it is difficult to achieve a small high-performance pressure sensor.
The present invention was created in order to solve this type of problem area, and the object thereof is to provide a small high-performance pressure sensor.